The present invention relates generally to circuit card assemblies, and more particularly to a new and improved signal cross-over interconnect for a double-sided circuit card assembly.
A double-sided circuit card assembly, adapted for military or other rugged-environmental usage, comprises a pair of printed wiring boards wherein signal interconnects from a first one of the printed wiring boards disposed upon a first side of the circuit card assembly to the second one of the printed wiring boards disposed upon a second side of the circuit card assembly are conventionally made by means of a flex circuit cross-over which is located upon, or is disposed around, one side edge portion of the double-sided circuit card assembly. More particularly, the end portions of the flex circuit cross-over are soldered to a row of pads located adjacent to an edge portion of each printing wiring board. Backpanel connectors and wedge-locks are normally used upon or dedicate the other edge portions of the circuit card assembly. Consequently, the one side edge portion of the circuit card assembly which is available for the flex circuit signal cross-over interconnects can only provide a limited number of interconnection sites.
In addition, in order for a signal line to be connected from a first one of the printed wiring boards to the second one of the printed wiring boards, the signal line must first be routed to the circuit card assembly edge portion upon which the flex circuit cross-over interconnect is located, and subsequently, the signal line must be routed from the circuit card assembly edge portion, having the flex circuit cross-over interconnect mounted thereon, to the particular or final destination defined upon the second one of the printed wiring boards. This routing of the signal lines to and from the edge portion of the circuit card assembly so as to define every cross-over connection is spatially uneconomical in that such a connection mode consumes or takes up valuable space or routing channels which could otherwise be used for circuit nets or circuit lines. This becomes a significant problem and operative limitation in connection with high-density circuit card assembly designs, systems, or arrays, wherein only a limited number of signal layers are available for routing, or still yet further, in connection with circuit card assembly designs with a relatively large number of circuit nets each of which requires a multiplicity of cross-over interconnect sites. It is also noted that the aforenoted conventional mounting of the flex circuit crossover interconnect upon or around the external edge portion of the circuit card assembly readily exposes the flex circuit cross-over interconnect to external environmental factors and potential damage. Accordingly, the interconnection flex circuit requires suitable provisions to be incorporated into the overall structure of the circuit card assembly in order to protect the external flex circuit cross-over interconnects from such external environmental factors and potential damage. The addition of such protective provisions add significant cost and time constraints to the circuit card assembly manufacturing procedures which further compromises production of such circuit card assemblies in an economical manner.
A need therefore exists in the art for a new and improved signal cross-over interconnect for a double-sided circuit card assembly wherein the structure of each double-sided circuit card assembly would be such that a significant improvement in the number of interconnection sites would be readily achieved, the actual connection of the signal lines between the two printed wiring boards would be significantly simplified, and the disposition of the flex circuit cross-over interconnect would be interposed between the pair of printed wiring boards so as to in effect be disposed internally of the double-sided circuit card assembly such that the flex circuit cross-over interconnect would be inherently protected or shielded from external environmental factors and potential damage whereby the need for auxiliary protection devices would be obviated.
Accordingly, it is an object of the present invention to provide a new and improved signal cross-over interconnect for a double-sided circuit card assembly.
Another object of the present invention is to provide a new and improved signal cross-over interconnect for a double-sided circuit card assembly which effectively over-comes the various drawbacks and disadvantages characteristic of the PRIOR ART double-sided circuit card assemblies.
An additional object of the present invention is to provide a new and improved signal cross-over interconnect for a double-sided circuit card assembly wherein the number of interconnection sites is significantly enhanced, and the actual connection of the signal lines between the two printed wiring boards is significantly simplified yet still reworkable.
A further object of the present invention is to provide a new and improved signal cross-over interconnect for a double-sided circuit card assembly wherein the disposition of the flex circuit cross-over interconnect is interposed between the pair of printed wiring boards so as to in effect be disposed internally of the double-sided circuit card assembly such that the flex circuit cross-over interconnect is inherently protected or shielded from external environmental factors and potential damage whereby the need for auxiliary protection devices would be obviated.
A last object of the present invention is to provide a new and improved signal cross-over interconnect for a double-sided circuit card assembly wherein the structure of the double-sided circuit card assembly is such that heat dissipation in connection with the pair of printed wiring boards is enhanced, while good mechanical support for the flex circuit cross-over interconnect is likewise provided.
The foregoing and other objectives are achieved in accordance with the teachings and principles of the present invention through the provision of a new and improved signal cross-over interconnect for a double-sided circuit card assembly which comprises a pair of printed wiring boards and a metal frame member fabricated, for example, from aluminum or a copper alloy, interposed between the two printed wiring boards. The metal frame member has a through-slot defined therein, and an internal edge portion of the frame member which defines the through-slot has a rounded or arcuate configuration such that a flex circuit component, having a plurality of dendritic contact pads mounted upon a substrate portion thereof in a predetermined array, can in effect be wrapped around such internal edge portion of the frame member and bonded to oppositely disposed upper and lower surface portions of the frame member. The dendritic contact pads formed or provided upon the flex circuit component are adapted to be mated with surface-mounted contact pads, formed or provided upon oppositely disposed surfaces of the pair of printed wiring boards, during the bonding operation securing the pair of printed wiring boards to opposite surface portions of the metal frame member, and in this manner, an integral double-sided circuit card assembly having a signal cross-over interconnect is fabricated.